AAMI recently published an updated version of ST79 - ANSI/AAMI ST79:2006 and A1:2008 and A2:2009. There are over 20 major changes to the document. One of them of note is the clarification of language related to double pouching. Section 8.3.4: Paper-Plastic Pouches clarifies the rationale related to the proper method for double pouching. When double pouching, two sequentially sized pouches should be used and the pouches should be positioned so that plastic faces plastic and paper faces paper.
The reason? Because the plastic laminate is impervious to the sterilant, so if the arranged plastic to paper (rather than plastic to plastic) the risk would be high that the sterilant would not reach the item inside. AAMI stresses that it is critical that the manufacturer of paper-plastic pouches provide validated documentation that their product can be used in a double-pouching configuration. We have more information below to help you use pouches properly.